Problem Playing Videos on Windows XP with Leadtek Graphics Card

Hi guys,

I'm experiencing a very strange problem with my PC at the moment. I
can't seem to play any videos, no matter what format they are! (MPEG,
WMV, AVI, DIVX, DVD, etc...)

Here are a few details about my setup:

ASUS A7N8X-E Deluxe motherboard
Leadtek WinFast A6600 GT graphics card (I think it has 128MB on board)
Creative Audigy Platinum soundcard

When I try and play videos, either the application crashes (as in the
case of Windows Media Player) or the application freezes and takes up
100% of my processor. In the later case, I have to painstakingly use
Task Manager to end the bad process. Painstaking because the naughty
video application only allows other Windows processes small chunks of
processor time.

Could this be a codex problem? Does any one have any suggestions!?

Thanks,

Steve.

P.S. Apologies if this is posted in the wrong place. Please suggest a
more suitable alternative!